Definition(s)
Postweld Heat Treatment
A work process which consists of heating an entire weldment or section of fabricated piping to an elevated temperature after completion of welding in order to relieve the detrimental effects of welding heat, such as reducing residual stresses, reducing hardness, and/or slightly modifying properties (See ASME B31.3, paragraph 331).
Source: API 570, Piping Inspection Code: In-service Inspection, Rating, Repair, and Alteration of Piping Systems, Fourth Edition, February 2016, with Addendum May 2017. Global Standards
Postweld Heat Treatment
Controlled heat treatment subsequent to welding, including stress relief to obtain desired material properties.
Source: API STANDARD 16AR, Standard for Repair and Remanufacture of Drill-through Equipment, First Edition, April 2017. Global Standards